Because pressure is required to stroke a bonded piston, its sealing lip will be pressurized during stroking. The standard practice is to design a sealing lip that will be highly sensitive to pressure to ensure that it will be pressure-activated and therefore will not leak. However, a higher degree of pressure actuation (as shown by the downward arrows) will result in a higher normal force under pressure and therefore a higher sliding load.
FIG. 1 shows a radial cross-sectional view of a prior art sealing lip. So, the prior art shows an increased pressure received area, which means increased pressure directly transferred to the sealing lip.
Accordingly, the problem to be solved by the present invention is reduced lip sliding friction. The present invention reduces the sliding load of a bonded piston by:
a. Reducing the pressure received area of the sealing lip; and
b. Reducing the static load of the sealing lip by eliminating rubber material on the back side of the sealing lip near the contact point. Lip integrity and ease of assembly (installation) is not compromised.
The invention works by drastically reducing the normal force exerted by the lip onto the lip running surface. This is achieved in two ways:
a. Reduction of sealing lip pressure received area. Because pressure is required to stroke the bonded piston, the sealing lip will be pressurized during stroking. The standard practice is to design a sealing lip that will be highly sensitive to pressure to ensure that it will be pressure-activated and therefore will not leak. However, a higher degree of pressure actuation will result in a higher normal force under pressure and therefore a higher sliding load.b. Elimination of material at the backside of the sealing lip near the contact point. This allows the lip to flex onto the running surface (either stretch onto a shaft or compress into a bore) much more easily because there is much less material to manipulate. This greatly reduces lip normal force.
FIG. 2 shows a radial cross-sectional view of a sealing lip of the present invention. As such, the present invention shows a reduced pressure received area, which means less pressure directly transferred to the sealing lip. Accordingly, the present invention solves this problem by providing a sealing lip that delivers a reduced pressure received area of the sealing lip and a reduced static load of the sealing lip by eliminating rubber material on a back side of the sealing lip near the contact point.